1. Field of Invention
The present invention relates to the field of transport vehicles, and more particularly but not by way of limitation, to an improved lock assembly for securing a trailer coupler.
2. Discussion
A common means of expanding the hauling capacity of land based vehicles is by the use of a wide variety of trailers, including utility or flatbed trailers, box trailers, livestock trailers and travel trailers. While there are several means for coupling a trailer to a vehicle, two of the most common are the fifth-wheel hitch and the rear-mounted hitch ball hitch assembly, the latter being perhaps the most popular. While the hitch ball portion of a hitch ball hitch assembly can vary in size and mounting location, the vehicle portion of most hitch ball hitching assemblies is generally constant. However, the trailer coupler that connects to the vehicle hitch ball varies greatly in design.
Due to variation in trailer couplers there have been numerous prior art devices designed for securing hitch ball hitch assemblies to prevent theft and accidental detachment of the trailer from the vehicle. Such security devices are generally of two broad types, box or canister devices that cover all or a portion of the coupler assembly and those that function to prevent a hitch ball from entering the coupler by restricting access to the operating mechanism. Examples of the first type are taught by U.S. Pat. No. 6,244,080 issued to Ray, et al.; U.S. Pat. No. 6,202,453 issued to Disher, et al.; U.S. Pat. No. 6,070,441 issued to Bernstrom; U.S. Pat. No. 5,937,679 issued to Villalon, Jr.; U.S. Pat. No. 5,794,961 issued to Niswanger; and U.S. Pat. No. 5,775,139 issued to Sellers. Patents that teach security devices that prevent hitch ball insertion into a trailer coupler include U.S. Pat. No. 5,410,893 issued to Easterwood; and U.S. Pat. No. 4,186,940 issued to Pillars.
A problem associated with these devices is that they can only be used when the trailer is detached from the vehicle. Thus, for protection against theft when the trailer is attached to a vehicle, another security device must be used. Additionally, when the trailer is attached to a vehicle, these devices must be stored, risking being lost or stolen.
Devices that lock a trailer to a towing vehicle comprise another category of security devices. Methods of functioning vary and include plate or chain devices permanently attached to either the vehicle or trailer. Examples of these latter mentioned devices are taught by U.S. Pat. No. 6,155,589 issued to Simpson; U.S. Pat. No. 6,062,583 issued to Lauricella, Jr.; U.S. Pat. No. 5,956,980 issued to Jenkins; U.S. Pat. No. 5,947,506 issued to Bauer; U.S. Pat. No. 5,873,271 issued to Smith; and U.S. Pat. No. 5,700,024 issued to Upchurch.
Depending upon the design, such security devices often require extensive and usually professional installation to either the vehicle or the trailer. Another problem associated with many of these devices, especially to vehicle mounted devices, is that they do not provide theft protection for the trailer when the trailer is not attached to a vehicle.
Yet another category of prior art security devices comprise those that simply lock the pre-existing latching mechanism of the hitch. Examples of such security devices are taught by U.S. Pat. No. 5,540,065 issued to Wyers; U.S. Pat. No. 5,284,038 issued to Johnson; and U.S. Pat. No. 4,711,106 issued to Johnson. The major problem associated with these security devices is that they cannot be used to lock certain types of sliding collar, or sleeve, hitches due to there being no provision for locking. As appearing herein, the words collar and sleeve will be interchangeable as such appears to the custom in the industry.
Some sliding collar trailer hitches do have a bore through the hitch neck for the insertion of a safety pin, but the placement of the accompanying lock makes these devices susceptible to accidental or intentional damage. Further, since the diameter of the bore that is usually provided is relatively small (usually one quarter inch or less), the pin on the lock has to be small and thus is easily sheared by one intent on defeating the security.
One additional prior art device is taught by U.S. Pat. No. 3,820,823, issued to Beaston for a sliding collar trailer hitch. The device is disposed in a slot and held in place horizontally by a padlock on one side and a flange on the other side, and it operates to block movement of the collar. A particular problem with the arrangement of this structure is that severance of the operating rod frees the device.
Finally, U.S. Pat. No. 5,582,420, issued to Ulbrich, teaches a method for retrofitting hitches of the type taught by U.S. Pat. No. 4,133,553, issued to Pierce, to accept a padlock. While this design does provide a locking method, the device is vulnerable to tampering or damage to the operating rod, the lever or the interface between the two to release the sliding collar. Additionally, modification of the hitch is required for its installation.